Antioxidant system based on an ascorbyl ester in combination with a complexing agent and a thiol and to compositions containing the same
The present invention relates to a new antioxidant system based on a stabilized ascorbyl ester containing, in combination, at least one complexing agent and at least one thiol, to the use of such an antioxidant system and to compositions based on oleoginous materials containing such a system and principally to cosmetic compositions. 
     It is known that fatty bodies have a tendency to oxidize, even at ambient temperature, and that this oxidation (or rancifying) imparts to them new characteristics, principally taste or odor. These characteristics are generally considered undesirable when these fatty bodies are incorporated, for example, in food compositions or in cosmetic compositions. 
     There is currently employed, in compositions containing fatty bodies, protective agents which, in fact, play the role of antioxidants. 
     Representative known and currently employed antioxidants include ascorbic acid which acts principally by the direct absorption of oxygen. However, ascorbic acid is only very slightly soluble in fatty bodies and is consequently employed only with difficulty for the protection of fatty bodies against oxidation. 
     In order to solubilize the ascorbic acid molecule in a fatty material, it has been proposed to use various ascorbyl esters such as, for example, ascorbyl stearate, palmitate or laurate; see for example the article of C.F. Bourgeois, &#34;Revue Francaise des Corps Gras&#34;, No. 9, pages 353-356 (September 1981). 
     It is known that, apart from their own antioxidant properties, ascorbic derivatives also have the characteristic of improving the activity of antioxidant agents such as tocopherols or caffeic acid and its esters, by favoring the regeneration of these antioxidant agents; see for example H.S. Olcott, &#34;Oil Soaps&#34;, 18, (1941), 77 and U.S. Pat. No. 2,462,663. 
     There has also been proposed the use of various improvements of these binary antioxidant agents, of the ascorbic derivative type+tocopherol or ascorbic derivatives+caffeic derivatives, by envisaging the addition of a third constituent, again to improve the antioxidant effects. Representative third constituents of these ternary systems, include principally p-aminobenzoic acid (U.S. Pat. No. 2,462,663), phospholipids (R.W. Riemenschneider et al, &#34;Oil Soap&#34;, 1944, 47) and amines (Klaui, &#34;The Functional (Technical) Uses of Vitamins&#34; ed. by M. Stein, University of Nottingham Seminar Vitamins, London, England, 1971, p. 110) etc. 
     It has now been discovered that it is possible to improve considerably the antioxidant properties of ascorbyl esters by using these antioxidants in conjunction with at least one complexing agent and at least one thiol. A significant synergistic effect is observed. 
     The present invention thus relates to a new antioxidant system based on at least one stabilized ascorbyl ester, characterized by the fact that it includes at least one complexing agent and at least one thiol in combination therewith. 
     The ascorbyl ester is certainly an ester which is soluble in the fatty body, and in particular an ester of an aliphatic acid having 6 to 24 carbon atoms, such as, for example, ascorbyl stearate, palmitate or laurate. 
     By complexing agent is meant a compound which is capable of inhibiting by chelation the catalytic effect of transition metals to the free state in the medium. 
     Representative useful complexing agents include principally, ethylene diamine tetracetic acid (EDTA), the pentasodim salt of diethylenetriamine pentacetic acid, hexadecylamine salicylate (HDAS), citric acid, tartaric acid and its sodium salt, phytic acid, dibenzyldithiocarbamate, or mixtures thereof. 
     In addition to at least one of these complexing agents, the composition of the present invention can also contain a secondary complexing agent such as sorbitol. 
     In accordance with the present invention, by thiol is meant a reducing compound which maintains the ascorbyl esters under their reduced form. 
     Representative thiols useful in the present invention, include in particular, N-acetyl cysteine, glutathion or a mixture thereof. 
     The new antioxidant system, such as defined above, can be provided principally in the form of an oily liquid composition; or again the antioxidant system can be provided in the form of an alcoholic solution such as an ethanolic solution. 
     In the antioxidant system of the present invention, the relative proportions of the three categories of principal constituents depend in particular on the molecular masses of the complexing agent and the thiol. Generally, the thiol is present at a rate of 1 to 37.5 percent and the complexing agent at a rate of 2 to 25 weight percent, relative to the total weight of these three types of constituents. 
     When a secondary complexing agent is employed at the same time as the principal complexing agent, it is present in an amount such that the mixture is present in an amount between 2 and 25 weight percent. 
     The ascorbyl ester is generally present in the antioxidant system having three constituents, in an amount between 5 and 87.5 weight percent. 
     The present invention also relates to an antioxidant system, such as defined above, that also contains another antioxidant selected from tocopherols and caffeic acid (or 3,4-dihydroxycinnamic acid) or its esters. 
     By &#34;tocopherols&#34; is meant not only α-tocopherol but also β-, γ- or δ-tocopherol as well as mixtures thereof. 
     Representative esters of caffeic acid include principally the alkyl esters such as the methyl, ethyl or butyl esters and the phytol ester. It has been noted, in a quite surprising manner, that, in such combinations, the antioxidizing activity of the tocopherols and caffeic acid result in a significant synergistic effect because of the presence of the ascorbyl ester stabilized by the complexing agent--thiol couple. 
     In accordance with this embodiment of the invention, the antioxidant system preferably comprises 0.5 to 20 weight percent tocopherol or caffeic acid (or an ester thereof); 8 to 70 weight percent of a complexing agent; and 2 to 30 weight percent of a thiol. 
     The molar ratio of the ascorbyl ester to the tocopherol or to caffeic acid or an ester thereof must be preferably greater than or equal to 3. 
     This synergistic effect can again be improved when the antioxidant system is based on a tocopherol in combination with a polypeptide. 
     In accordance with this embodiment of the invention, the amount of polypeptide is preferably between 1.5 and 80 weight percent. 
     The weight ratio of the polypeptide to the tocopherol must be preferably greater than or equal to 3. 
     The polypeptides have an average molecular weight between about 1,000 and about 100,000. Representative polypeptides include, in particular, the following: 
     (a) the polypeptide sold under the trade name &#34;KERASOL&#34; by Societe Croda Chemicals Ltd. (polypeptide of soluble keratin having an average molecular weight of about 100,000); 
     (b) the polypeptide sold under the trade name &#34;Polypeptide SF&#34; by Societe Naarden (polypeptide of partially neutralized animal collagen having an average molecular weight of about 1000); 
     (c) the polypeptide sold under the trade name &#34;Polypeptide LSN&#34; by Societe Naarden (polypeptide of animal collagen in the form of the ammonium salt containing about 3 percent (max.) of inorganic salt); and 
     (d) the polypeptide sold under the trade name &#34;LACTOLAN&#34; by Laboratories Serobiologiques de Nancy (polypeptide obtained from fresh cow milk previously delipidated). 
     The present invention also relates to compositions containing fatty bodies characterized by the fact that they include at least one antioxidant system such as defined above. 
     The compositions of the present invention can be, principally, food compositions (edible oils, lard, butter, margarine or other butter substitutes) or cosmetic compositions. 
     The fatty bodies present in the cosmetic compositions of the present invention are, for example, fatty bodies of animal origin such as cetin (spermaceti), beeswax, lanolin, perhydrosqualene, turtle oil, etc; vegetable fatty bodies in the form of oils, fats or waxes such as sweet almond oil, avocado oil, olive oil; copra oil or hydrogenated African palm oil, cocoa butter, Carnauba wax, Montan wax; as well as synthetic oils constituted by esters and/or ethers of glycerol or glycol such as, for example, those which are described in French Patent Nos. 75.24656, 75.24657 and 75. 24658. 
     In addition to more or less oxidizable fatty bodies, the cosmetic composition can contain products sensitive to oxidation such as, for example, vitamin F or β-carotene. 
     The cosmetic compositions according to the present invention are provided in the form of oily solutions, emulsions, solid products or lotions. They constitute, principally, milks for the care of the skin, creams (face creams, hand creams, body creams, anti-sun creams, make-up remover creams, dye foundation creams), liquid dye foundations, makeup remover milks, anti-sun milks, bath oils, lip rouge, eyelid shadow, deodorant sticks, etc. 
     In accordance with a preferred embodiment, the cosmetic compositions are provided in the form of creams intended for the protection of skin lipids against oxidation. 
     In the cosmetic compositions according to the present invention, the antioxidant system, such as defined above, is generally present such that it has the following proportions relative to the total weight of the compositions: tocopherol or caffeic acid (or an ester thereof), 0 to 0.5 percent and preferably, 0.05 to 0.5 percent; ascorbyl ester, 0.45 to 1.6 percent; complexing agent, 0.2 to 0.5 percent; and thiol, 0.1 to 0.7 percent. 
     When the antioxidant system is based on tocopherol the amount of polypeptide optionally present is between 0.05 to 8 percent relative to the total weight of the composition. 
     The compositions of the present invention can also contain active components or components conventionally employed in the compositions mentioned above, such as surfactants, dyes, perfumes, astringents, U.V. absorbers, organic solvents, water, etc. 
     These compositions are prepared in accordance with conventional procedures. 
    
    
     The following nonlimiting examples are given to illustrate several antioxidant systems in accordance with the present invention, as well as cosmetic compositions containing such antioxidant systems. 
     EXAMPLE 1 
     
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Ascorbyl palmitate                                                        
                76 wt. percent                                            
Citric acid     16 wt. percent                                            
N-acetyl cysteine                                                         
                 8 wt. percent                                            
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     EXAMPLE 2 
     
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Ascorbyl palmitate                                                        
                73 wt. percent                                            
Citric acid     9 wt. percent                                             
Glutathion      9 wt. percent                                             
N-acetyl cysteine                                                         
                9 wt. percent                                             
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     EXAMPLE 3 
     
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Ascorbyl palmitate                                                        
                79 wt. percent                                            
Citric acid      5 wt. percent                                            
EDTA            12 wt. percent                                            
N-acetyl cysteine                                                         
                 4 wt. percent                                            
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     EXAMPLE 4 
     
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Tocopherols (mixture of α-, β-, γ-                       
                       7 wt. percent                                      
and δ-tocopherols)                                                  
Ascorbyl palmitate     65 wt. percent                                     
Citric acid            7 wt. percent                                      
EDTA                   13 wt. percent                                     
N-acetyl cysteine      8 wt. percent                                      
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     EXAMPLE 5 
     
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Tocopherols       11 wt. percent                                          
Ascorbyl palmitate                                                        
                  65 wt. percent                                          
Hexadecylamine salicylate                                                 
                  6 wt. percent                                           
Sorbitol          9 wt. percent                                           
N-acetyl cysteine 9 wt. percent                                           
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     EXAMPLE 6 
     
         ______________________________________                                    
Tocopherols     16 wt. percent                                            
Ascorbyl palmitate                                                        
                63 wt. percent                                            
Glutathion      6 wt. percent                                             
N-acetyl cysteine                                                         
                3 wt. percent                                             
Citric acid     3 wt. percent                                             
EDTA            9 wt. percent                                             
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     EXAMPLE 7 
     
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Caffeic acid     8 wt. percent                                            
Ascorbyl palmitate                                                        
                49 wt. percent                                            
Citric acid      4 wt. percent                                            
EDTA            10 wt. percent                                            
Glutathion      10 wt. percent                                            
N-acetyl cysteine                                                         
                19 wt. percent                                            
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     EXAMPLE 8 
     
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Caffeic acid     7 wt. percent                                            
Ascorbyl palmitate                                                        
                65 wt. percent                                            
Sodium tartrate  8 wt. percent                                            
N-acetyl cysteine                                                         
                20 wt. percent                                            
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     EXAMPLE 9 
     
         ______________________________________                                    
Caffeic acid       8 wt. percent                                          
Ascorbyl palmitate                                                        
                  70 wt. percent                                          
Hexadecylamine salicylate                                                 
                  15 wt. percent                                          
N-acetyl cysteine  7 wt. percent                                          
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     EXAMPLE 10 
     
         ______________________________________                                    
Tocopherols           9 wt. percent                                       
Ascorbyl palmitate    36 wt. percent                                      
Citric acid           4.5 wt. percent                                     
N-acetyl cysteine     4.5 wt. percent                                     
EDTA                  1.5 wt. percent                                     
&#34;KERASOL&#34;, polypeptide                                                    
                      44.5 wt. percent                                    
(active material)                                                         
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     EXAMPLE 11 
     
         ______________________________________                                    
Tocopherols           5 wt. percent                                       
Ascorbyl palmitate    21.5 wt. percent                                    
Citric acid           2.5 wt. percent                                     
N-acetyl cysteine     1 wt. percent                                       
Glutathion            1 wt. percent                                       
EDTA                  2.5 wt. percent                                     
&#34;Polypeptide SF&#34;, polypeptide                                             
                      66.5 wt. percent                                    
(active material)                                                         
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Examples of Cosmetic Compositions                                         
Example I - Skin cream (water-in-oil emulsion)                            
______________________________________                                    
Magnesium lanolate    14.4 wt. percent                                    
Lanolin alcohol       3.6 wt. percent                                     
Turnsole oil          40.0 wt. percent                                    
Isopropyl myristate   8.0 wt. percent                                     
Ozokerite             4.0 wt. percent                                     
Vitamin F             2.0 wt. percent                                     
Ascorbic acid         0.5 wt. percent                                     
Soy lecithin          5.0 wt. percent                                     
Tocopherols           0.25 wt. percent                                    
Ascorbyl palmitate    1.0 wt. percent                                     
Glutathion            0.1 wt. percent                                     
N-acetyl cysteine     0.05 wt. percent                                    
Citric acid           0.05 wt. percent                                    
EDTA                  0.15 wt. percent                                    
Perfume               0.8 wt. percent                                     
Methyl parahydroxybenzoate                                                
                      0.3 wt. percent                                     
Water, sufficent amount for                                               
                      100 wt. percent                                     
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         ______________________________________                                    
 Example II - Anhydrous Balm                                              
______________________________________                                    
Karite oil             60.0 wt. percent                                   
Turnsole oil           20.0 wt. percent                                   
Vitamin F              2.0 wt. percent                                    
Soy lecithin           4.9 wt. percent                                    
Tocopherols            0.2 wt. percent                                    
Ascorbyl palmitate     1.13 wt. percent                                   
Glutathion             0.35 wt. percent                                   
Citric acid            0.15 wt. percent                                   
N-acetyl cysteine      0.35 wt. percent                                   
EDTA                   0.15 wt. percent                                   
Petrolatum, sufficient amount for                                         
                       100 wt. percent                                    
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         ______________________________________                                    
 Example III - Face and body oil                                          
______________________________________                                    
Karite oil             2.0 wt. percent                                    
Turnsole oil           31.8 wt. percent                                   
Vitamin F              2.0 wt. percent                                    
Soy oil                32.0 wt. percent                                   
Tocopherols            0.1 wt. percent                                    
Citric acid            0.05 wt. percent                                   
Ascorbyl palmitate     1.0 wt. percent                                    
N-acetyl cysteine      0.1 wt. percent                                    
EDTA                   0.15 wt. percent                                   
Soy lecithin           0.1 wt. percent                                    
Peanut oil, sufficient amount for                                         
                       100 wt. percent                                    
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 Example IV - Skin care cream (oil-in-water emulsion)                     
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Sorbitan monostearate having                                              
                      1.0 wt. percent                                     
20 moles of ethylene                                                      
oxide (&#34;Tween 60&#34;)                                                        
Glycerol stearate     2.0 wt. percent                                     
Stearic acid          1.4 wt. percent                                     
Triethanolamine       0.7 wt. percent                                     
Cetyl alcohol         0.5 wt. percent                                     
Turnsole oil          15.0 wt. percent                                    
Vitamin F             2.0 wt. percent                                     
Ascorbic acid         1.0 wt. percent                                     
Soy lecithin          0.6 wt. percent                                     
Petrolatum oil        2.4 wt. percent                                     
Caffeic acid          0.2 wt. percent                                     
Ascorbyl palmitate    1.5 wt. percent                                     
Hexadecylamine salicylate                                                 
                      0.5 wt. percent                                     
N-acetyl cysteine     0.3 wt. percent                                     
Carboxy vinyl polymer, sold                                               
                      0.2 wt. percent                                     
under the name &#34;Carbopol                                                  
940&#34; by Goodrich                                                          
Triethanolamine       0.2 wt. percent                                     
Perfume               0.8 wt. percent                                     
Preservative (methyl  0.25 wt. percent                                    
parahydroxybenzoate)                                                      
Water, sufficient amount for                                              
                      100 wt. percent                                     
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Example V - Body care fluid                                               
______________________________________                                    
1st phase                                                                 
Non-ionic amphiphilic lipid having the formula,                           
                         4.5 wt. percent                                  
 ##STR1##                                                                 
wherein R is a hexadecyl radical and n has a                              
statistic average value equal to 3                                        
Cholesterol              4.5 wt. percent                                  
Dicetylphosphate         1.0 wt. percent                                  
Methyl parahydroxybenzoate                                                
                         0.3 wt. percent                                  
Sterile demineralized water                                               
                         30.0 wt. percent                                 
2nd phase                                                                 
To the dispersion of spherules obtained in the first phase,               
the following components are added.                                       
Perfume                  0.4 wt. percent                                  
Turnsole oil             10.0 wt. percent                                 
Paraffin oil             4.0 wt. percent                                  
Vitamin F                2.0 wt. percent                                  
Soy lecithin             1.0 wt. percent                                  
Caffeic acid             0.1 wt. percent                                  
Ascorbyl palmitate       1.0 wt. percent                                  
Hexadecylamine salicylate                                                 
                         0.2 wt. percent                                  
N-acetyl cysteine        0.1 wt. percent                                  
Carboxy vinyl polymer, sold under the name                                
                         0.4 wt. percent                                  
&#34; Carbopol 940&#34;  by Goodrich                                              
Triethanolamine          0.4 wt. percent                                  
Demineralized water, sufficient amount for                                
                         100 wt. percent                                  
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 Example VI - Solar cream                                                 
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Magnesium lanolate     7.2 wt. percent                                    
Lanolin alcohol        1.8 wt. percent                                    
Turnsole oil           20.6 wt. percent                                   
Vitamin F              2.0 wt. percent                                    
β-carotene        0.1 wt. percent                                    
Soy lecithin           0.4 wt. percent                                    
Paraffin oil           4.0 wt. percent                                    
Caffeic acid           0.1 wt. percent                                    
Ascorbyl palmitate     0.4 wt. percent                                    
Citric acid            0.05 wt. percent                                   
Glutathion             0.05 wt. percent                                   
N-acetyl cysteine      0.05 wt. percent                                   
EDTA                   0.15 wt. percent                                   
Ascorbic acid          1.0 wt. percent                                    
Polyethylene powder    10.0 wt. percent                                   
2-phenyl-5-benzimidazole                                                  
                       3.0 wt. percent                                    
sulfonic acid, sold under                                                 
the name &#34;EUSOLEA 232&#34;                                                    
by Merck                                                                  
2-hydroxy-4-methoxy benzophenone,                                         
                       3.0 wt. percent                                    
sold under the name                                                       
&#34;UVINUL M40&#34; by BASF                                                      
Perfume                1.0 wt. percent                                    
Methyl parahydroxybenzoate                                                
                       0.15 wt. percent                                   
Propyl parahydroxybenzoate                                                
                       0.15 wt. percent                                   
Water, sufficient amount for                                              
                       100 wt. percent                                    
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 Example VII - Face and body oil                                          
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Karite oil             2.0 wt. percent                                    
Turnsole oil           31.8 wt. percent                                   
Vitamin F              2.0 wt. percent                                    
Soy oil                32.0 wt. percent                                   
Tocopherols            0.3 wt. percent                                    
Citric acid            0.15 wt. percent                                   
Ascorbyl palmitate     1.2 wt. percent                                    
N-acetyl cysteine      0.15 wt. percent                                   
EDTA                   0.05 wt. percent                                   
&#34;KERASOL&#34;, polypeptide 1.5 wt. percent                                    
(active material)                                                         
Soy lecithin           0.1 wt. percent                                    
Peanut oil, sufficient amount for                                         
                       100 wt. percent                                    
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 Example VIII - Skin care cream (water-in-oil emulsion)                   
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Magnesium lanolate    14.4 wt. percent                                    
Lanolin alcohol       3.6 wt. percent                                     
Turnsole oil          40.0 wt. percent                                    
Isopropyl myristate   8.0 wt. percent                                     
Ozokerite             4.0 wt. percent                                     
Vitamin F             2.0 wt. percent                                     
Ascorbic acid         0.6 wt. percent                                     
Soy lecithin          5.0 wt. percent                                     
Tocopherols           0.2 wt. percent                                     
Ascorbyl palmitate    0.9 wt. percent                                     
Glutathion            0.05 wt. percent                                    
N-acetyl cysteine     0.05 wt. percent                                    
Citric acid           0.1 wt. percent                                     
EDTA                  0.1 wt. percent                                     
&#34;Polypeptide SF&#34;, polypeptide                                             
                      2.8 wt. percent                                     
(active material)                                                         
Perfume               0.8 wt. percent                                     
Methyl parahydroxybenzoate                                                
                      0.3 wt. percent                                     
Water, sufficent amount for                                               
                      100 wt. percent                                     
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     1. Stabilization study of ascorbyl palmitate 
     In order to determine the stabilization effect of the complexing agent--thiol couple on ascorbyl palmitate, several solutions in ethanol have been studied. 
     The determination, over time, of the amount of degradation of ascorbyl plamitate has been effected by HPLC. 
     The solutions studied were the following: 
     Solution A--Ascorbyl palmitate, 0.05 wt. percent; 
     Solution B--Ascorbyl palmitate, 0.05 wt. percent, 
     N-acetyl cysteine, 0.01 ; 
     Solution C--Ascorbyl palmitate, 0.05 wt. percent 
     EDTA, 0.01 
     Solution D--Ascorbyl palmitate, 0.05 wt. percent 
     N-acetyl cysteine, 0.01 
     EDTA, 0.01 
     The results obtained are shown on FIG. 1. 
     As can be noted, as a function of the curve corresponding to Solution D, the amount of degradation of ascorbyl palmitate is considerably lower than the other solutions which demonstrates the stabilizing character of the complexing agent (EDTA)--thiol (N-acetyl cysteine) couple. 
     In effect, at the end of 40 days, the amount of degradation of ascorbyl palmitate in Solution D is only about 30 percent whereas for Solutions A, B and C, the ascorbyl palmitate is completely degraded at the end of the same time period. 
     2. Study of the synergism effect between ascorbyl palmitate, stabilized by a mixture of HDAS+N-acetyl cysteine, and tocopherols 
     The oil employed in this study is vitamin F. 
     Mixtures of vitamin F with various amounts of tocopherols, ascorbyl palmitate, hexadecylamine salicylate (HDAS) and N-acetyl cysteine have been prepared. The amounts of each component are set forth in Table I below; they are expressed in percent and are relative to the same amount (100 g) of vitamin F. 
     Each sample being studied is heated to 100° C. under a bubbling of air (20 1/hr) so as to effect accelerated oxidation of the oil. 
     The concentration of volatile acids, resulting from the degradation of the hydroperoxides and aldehydes, formed by oxidation, is continuously followed in a cell filled with water into which is inserted a platinum electrode. This electrode measures the evolution of the conductivity as a function of time. Oxidation causes an increase in the conductivity. 
     The induction time, which represents the time at the end of which oxidation begins, is determined by the intersection of the two tangents at the self-oxidation curve. 
     
                       TABLE I                                                     
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Ascorbyl          N-acetyl            Induction                           
palmitate                                                                 
       HDAS*      cysteine Tocopherols                                    
                                      Time                                
______________________________________                                    
--     --         --       0.20       60 min.                             
0.20   --         --       --         20 min.                             
0.20   --         --       0.20       92 min.                             
--     0.20       0.10     --         15 min                              
0.20   0.20       --       0.20       93 min.                             
0.20   --         0.10     0.20       96 min.                             
0.20   0.20       0.10     0.20       114 min.                            
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 *hexadecylamine salicylate                                               
 
    
     The induction time of vitamin F, alone, without an antioxidant is 15 minutes. 
     Table I shows that the combination of hexadecylamine salicylate and N-acetyl cysteine, alone produces no effect. On the other hand, as is known, the combination of α-tocopherol and ascorbyl palmitate leads to a significant increase in the induction time. This induction time is again significantly improved by the combination of hexadecylamine salicylate+N-acetyl cysteine although each of these two agents added alone to an α-tocopherol+ascorbyl palmitate mixture is practically without influence. 
     3. Study of the synergism effect between ascorbyl palmitate, stabilized by a mixture of HDAS+N-acetyl cysteine and caffeic acid 
     The procedures set forth in part 2, above, are repeated. The results are given in Table II, below. 
     
                       TABLE II                                                    
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Ascorbyl          N-acetyl   Caffeic                                      
                                   Induction                              
palmitate HDAS    cysteine   Acid  Time                                   
______________________________________                                    
0.25      --      --         0.10   93 min.                               
0.21      0.21    0.10       0.10  315 min.                               
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     Table II shows the synergism effect achieved by the addition, to the system studied, of the combination of hexadecylamine salicylate - N-acetyl cysteine. 
     This combination considerably increases the induction time of the caffeic acid+ascorbyl palmitate system, although used alone, this combination, as has been shown in Table I, above, has no effect.